JPS58202948A - Casting method of cast steel - Google Patents

Abstract

PURPOSE:To improve the internal characteristics of a casting by forming desired ruggedness which divides the shrinkage stress of a casting surface on the chill surface of a chiller used on part or the whole surface of a casting mold and casting cast steel. CONSTITUTION:Grooves 3 of an orthogonal grid-like shape are provided on the chill surface 2 of a chiller 1 used on part or the whole surface of a casting mold in the stage of casting cast steel by taking the stress acting in the two directions such as vertical and horizontal or perpendicular directions into consideration. A casting surface 4 which is the site for large shrinkage stress on solidification is divided to the small stress sites of every range enclosed by the gooves 3, by which the cracking of the casting mold is prevented. If the angle assumed by the side wall 5 of the gooves 3 and the surface 2 is near 90 deg., the restraining of the surface 4 by the grooves 3 becomes too strong and the periphery of the grooves 3 is vulnerable to generate the point where the shrinkage stress of the surface 4 concentrates; therefore, said angle is to be kept at >=120 deg.. The radius R of curvature of the roundness in the angle corner part 6 assuming the intersected point of the side wall 5 and the surface 2 is to be set at the depth F of the grooves 3 or above.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a cooling metal for cast steel used on a part or the entire surface of a mold for the purpose of improving the internal properties of a steel casting.

Cast steel products have the advantage of fewer restrictions on shape than rolled or forged products, but when cast into sand molds,
As products become larger and more complex in shape, they have the disadvantage that internal defects inevitably occur inside the ingot due to the solidification phenomenon.

Conventionally, as a preventive measure, in order to control the solidification conditions within the cast steel, an iron block or steel block, usually called a chiller, was used on the mold surface, and the ingot part facing the block was cooled. A method of promoting coagulation is used,
It has been effective in improving the internal quality of cast steel.

However, it has been empirically recognized that cracks are likely to occur on the surface of cast steel products when exposed to a cold metal, and that the larger the cast steel product is, the larger the surface area of the cold metal, the greater the tendency for cracks to occur. The following phenomena are listed as the causes of this phenomenon.

In other words, the difference between applying a chill mold to cast steel and a sand mold is that the goose bump surface that the chill metal touches is rapidly cooled, and shrinkage stress due to solidification occurs rapidly, and the cold metal is a lump of metal. However, the cooling metal does not follow the deformation caused by solidification shrinkage of cast steel at all, but rather expands due to temperature rise, exhibiting behavior that is opposite to the solidification shrinkage of cast steel.

It acts in a direction that promotes cracking of the casting surface.

In addition, to prevent cracking of the casting surface where cold metal is applied,
Conventionally, there is a method of sanding, but sanding causes a problem in that the effect of improving the internal properties of cast steel by chilling metal is significantly reduced due to the heat insulating properties of sand.

Conventionally, there was no appropriate method to prevent surface cracking when using this cooling metal, and solvents and welding repairs were indispensable to remove cracks that occurred on the casting surface, and manufacturing costs and processes were high. This has caused significant losses, and there is a need to establish a method to prevent this.

Techniques for preventing cracking on the casting surface include flute or corrugated molds for rolling and casting steel ingots. The cross-sectional shape of these steel ingots is simple, square, rectangular, or circular when viewed macroscopically, and cracks that occur as the steel ingot solidifies occur on the outer periphery and in the height direction of the steel ingot. Therefore, it is known that the inner surface of the mold is provided with unevenness in only one direction parallel to the axis of the steel ingot.

What is the uneven shape of a flute or corrugate?

Generally, the steel ingot is constructed with a complex curve taking into consideration the shrinkage situation of the steel ingot, and as a result, so-called vertical cracking of the steel ingot skin is thought to be almost completely prevented.

However, in cast steel, the cast surface that is in contact with the cold metal is
Cracking occurs even though the area of the mold for steel ingots, which requires flutes or corrugations, is much smaller, and the reason for this is that the shape of the cast steel is more complex than that of steel ingots, and it is difficult for the steel to hit the cold metal. This is due to the fact that stress in multiple directions on the casting surface must be considered. It is well known that stress is vector-combined, and when the resultant force of stresses acting in multiple directions exceeds the proof stress, the direction of the resultant force is
1. It is inevitable that cracks will occur in the right angle direction.

That is, regarding the surface of the cast steel that is in contact with the cooling metal, consideration must be given to dealing with stress in multiple directions.

The present invention was completed as a result of detailed analysis of the shrinkage stress of the casting surface during cast steel casting from the above-mentioned points. The purpose of this method is to form desired unevenness on the chilled metal surface to divide the shrinkage stress of the casting surface before casting.

It is well known that cracking generally occurs when the stress applied to that part exceeds its proof stress, and in order to prevent cracking, it is necessary to increase the proof stress or reduce the stress. In the case of cast steel, its yield strength is determined by the range required by one material characteristic of the product, and it is impossible to adjust the yield strength only on the as-cast surface during casting.

Also, from the point of view of tensile stress acting on the casting surface during casting, this stress is generated due to solidification shrinkage.
The shape and width of the as-cast surface of the cast steel determine the total amount on that surface, and it is impossible to increase or decrease it arbitrarily. If the size of the chiller is small, the total amount of stress generated on the casting surface that the chiller touches is small, so cracks will not occur.

In other words, according to the research conducted by the present inventors, when a chiller with a width and length of less than 200 Jll1 (hereinafter referred to as a small chiller) is used alone, the casting caused by the chiller is Although there is no concern about cracking of the skin, if multiple of these small chillers are arranged side by side to form an aggregate, and either the width or length exceeds 200 m5 (hereinafter, these are referred to as large chillers). (referred to as gold) is used.

-Skin sensitivity to cracks increases rapidly. The magnitude of the stress that causes this cracking is reduced by the cooling effect on the casting surface.

In other words, measures aimed at reducing the thickness of the chiller and the area of the chiller applied to one radiation surface ignore the aim of improving the internal properties of cast steel through the cooling effect of the chiller. This is putting the cart before the horse. In order to prevent internal defects in cast steel, it is necessary to use a chiller of the necessary thickness and width, that is, a large chiller, and in addition, measures to prevent cracking on the casting surface that the chiller touches are necessary. There must be.

Based on the above-mentioned study on the cracking of the caraded surface of cast steel that has been applied with a cold metal, the present inventors dispersed the stress acting on the skin in multiple directions and calculated the absolute value of the combined stress. As a means of keeping the cost below the financial strength of cast steel and thereby preventing the occurrence of cracking on the casting surface,
The idea was to create a casting method for cast steel that creates concavities and convexities that form a continuous pattern not only in one direction but in multiple directions.

The details of the present invention will be explained below with reference to the drawings.

Figure 1 is an example of a large flat chiller that embodies the basic idea of the present invention. , is a method in which orthogonal lattice-shaped grooves 3 are provided on the entire cooling surface 2 that is in contact with the casting surface 4 of the cooling metal 1, thereby reducing the casting surface 4, which is a large solidification shrinkage stress field, to the area surrounded by the grooves. By dividing the stress field into each small stress field and making the absolute value of the stress in the divided stress field a sufficiently small value within the financial limit of the cast skin 4, The purpose is to prevent cracking.

In this case, the grooves serve to divide the casting surface into small stress fields, and grooves that are too shallow are ineffective for this purpose. As shown in FIG. 2, the depth F of the groove varies depending on the casting conditions at the time, but it has been confirmed through experiments by the present inventors that in normal casting, a depth F of approximately 5III+ or more is sufficient.

At the same time, if the angle between the side wall 5 of the groove 3 and the cooling surface 2 is close to 90 degrees, the restriction of the casting surface 4 by the groove 3 will be too strong, causing a concentration point of shrinkage stress of the casting surface 4 around the groove 30. It has been found that this angle usually needs to be 120 degrees or more, and preferably around 135 degrees, in order to facilitate manufacturing.

Furthermore, in a state where the intersection line between the side wall 5 of A3 and the cooling surface 2 forms a ridgeline with a clear angle, this ridgeline is transferred to the casting surface 4, and the corner portion 6 acts as an edge for the stress generated on the casting surface 4. Corners 6 must be smoothly rounded, as this will actually encourage the occurrence of dents. It was confirmed that in order to expect a stress relaxation effect, the radius of curvature R' of the roundness should be equal to or more than the depth of the groove 3.

In addition to the above, the grooves increase the surface area of the cast steel and provide a shrinkage allowance for the cast surface to relax the shrinkage stress of the cast surface due to hardening and temperature reduction. The angle of the side wall of the groove and the roundness of the ridgeline where the groove and the cooling surface intersect serve the purpose of smoothing the shrinkage of the casting surface.

Moreover, the factors that determine the shrinkage margin of the cast surface 4 are mainly the groove depth F and the groove interval A. The curvature of the groove edge is a secondary factor, but although it has a large effect on the stress concentration described above, it has a small effect on increasing the casting surface area as a shrinkage margin. In experiments conducted by the present inventors, it has been found that the following conditions are necessary to prevent cracking of the cast surface 4.

[Groove spacing/Groove depth] [Remaining cooling surface after cutting] (1)
Outside side cooling metal...within 20 times, within 80% (
2) Inner side chiller: 12 times or less, 70% or less (3) Bottom side chiller: 12 times or less, 70% or less This is due to the formation of air gear lag due to solidification shrinkage of cast steel. Further, although it is not necessarily necessary to satisfy the above two conditions at the same time, it is desirable to satisfy both conditions.

Figure 3 shows the effect of preventing cracking on the casting surface when lattice-like grooves are formed on the entire surface of a large flat cooling chamber according to the procedure described above, and when this is actually used for casting products.

(The diagonal lines in the figure indicate the amount of repair due to cracking.) If the above-mentioned precautions are taken, the cracking of the casting surface that comes into contact with the chiller will be significantly reduced. Also, the lattice grooves mentioned above regarding the cylindrical outer mold? It was confirmed that the same results as the large planar chiller were obtained when using the attached chiller.

However, when using a cylindrical medium pre-cooled metal or a spherical cooled metal, the stress state becomes more complex due to the impact on the casting surface, and the direct lattice type groove is insufficient to prevent cracking on the casting surface. It turns out.

As a result of considering countermeasures, we came up with the idea of dividing the stress generated in the casting surface 4 into three directions, for example, or a large direction, and as shown in Figs. As shown in Fig. 4 a), or by cooling the grooves 3 forming a continuous hexagonal pattern (Fig. 4 b) on the entire surface 2, or (Fig. 4 0) and Fig. 4 d), for example, a triangular Or a cone or truncated cone (Figure 6a), or a spherical or truncated spherical surface (6th
This was realized by the method shown in Figure b).

In this case, the intervals between the grooves 3 and the recesses 8, the roundness of the green, etc. are the same as in the case of the lattice grooves (FIGS. 1 and 2). (In this case, the point is to disperse the stress,
Depending on the case, a pentagonal or hexagonal shape may also be used. ) Also, in some cases, cold metal may weld with the molten steel that has been cast. The bath coat phenomenon can be prevented by applying a coating agent to the cold metal surface. However, the cold metal surface is coated with a material with low thermal conductivity.

The effect of cooling cast steel and improving its internal quality using a cold metal is completely destroyed. Therefore, it is necessary to make the coating thickness vi of the mold coating agent as thin as possible, and according to the studies conducted by the present inventors, the coating thickness 'I'.

Care must be taken not to exceed 5 units. As long as this point is adhered to, it is permissible to apply the mold coating agent f to the cooling metal which has been subjected to the anti-cracking measures according to the present invention.Hereinafter, embodiments of the present invention will be described.

Example 1 An example in which the cooling metal of the present invention is applied to a thick part of cast steel with uneven wall thickness is shown below.

Applicable products: Upper plate type cast steel products with support lugs (Top plate mold part wall thickness 2005m.

Casting weight: 120 tons) Material: 5C49 (0.25%, 0.40%81
s 0.95%Mn) Product shape: Top plate-like hemispherical inner radius: 1550iIII Support lug dimensions: Length: 400m, bottom: 400m, top: 10
0111. Width 500m Applicable conditions of chiller Applicable range: Sabotrag Side and bottom cooling total thickness 2 1001Il Total area of chiller: 400X500M Cutting type into chiller... straight cross groove l Cutting shape... groove Depth: 25M groove Width: 501m Groove edge curvature: 5 pieces 1w Groove spacing: 250 Dragon The results of Example 1 were: - The skin was in good condition with no cracks, and the support lug part showed no defects as a result of radiation testing. Good quality was obtained.

Example 2
＃Continuous triangular pattern triangle which is one of the present invention
・Cold metal with a cone at the top is used over the entire core.
- Indicates the manufacturing results of cast steel products.

Target product: Arc-shaped cast steel product with ribs (product thickness 250M% casting weight 21t 600) Material: 5C49 (ci, 25%C, 0.40%Si, 0
．． 94%Mn) Shape: Overall width 1935IIjI, cylindrical surface width 1635M, Lip 11111i150 Dragon.

Product length 1800im, radius of 9 in cylinder 1550m
Application situation of cold metal Application range: Full metal molding of the inner casting surface of the cylindrical part of the product Total thickness: 500 Type of cut into fin cold metal: Triangular apex cold metal with continuous triangular pattern Cutting shape: 110jIjφ, depth 4511
1+ Center spacing of conical cut: 3 m+ per pot+ As a result of carrying out the above procedure, the distribution of stress in three or six directions on the casting surface is as follows: - In the cylindrical core chiller or the spherical chiller, This method is even more effective than the stress dispersion method in the leftward direction, and the need for maintenance and repair of the casting surface to remove cracks is further reduced to virtually zero. The situation is shown in Figure 5. (The shaded area in the figure indicates repair due to cracking.) Example 3 Example of using violet molding agent Target product: Thick plate flat casting product Thickness 2001m, width 1B00m, length 2500m Material 5C46 (0.2% C, 6.40%Si, 0.8
0%Mn) Bottom flat plate integrated cooling All applicable cooling Total thickness: 300m% Width 1800m, length 2500a
Measures to prevent cracking: Orthogonal cross-groove groove depth: 25 mm, purchase @: 5 o dragon groove spacing: 250 mm Under these conditions, coating agents were used as shown in Table 1.

As can be seen from Table 1, even when the coating agent was applied, no cracking occurred and there was no change in the healthy layer.

As mentioned above, it is possible to provide grooves that form a continuous pattern such as a lattice shape or a triangular or hexagonal shape on the entire surface of the cooled cast steel, and furthermore, to form grooves that form a continuous pattern or form a conical or truncated cone or By providing spherical or truncated spherical recesses, it is an extremely effective industrial means to prevent cracking when using a wide area chiller for the purpose of improving the internal quality of cast steel. As a result, the time required for maintenance and repair of the casting surface, which has a significant impact on the cost and construction period of cast steel, is greatly reduced, making this an extremely useful invention.

In addition to the above-mentioned method, the present invention is also applicable to casting using an outer mold, and this does not, of course, deviate from the scope of the present invention.

Although the present invention has been described above, the embodiments of the present invention are as follows.

1. A chiller used for a part or the entire surface of a mold when casting steel, the width and length of which are each 200 + s+ or more when one or more molds are lined up. Orthogonal lattice grooves are provided on the entire surface (the surface in contact with the casting surface), and several side walls have an angle between vertical and horizontal with respect to the cooling surface, and the angle between the side wall and the cooling surface is A method of casting steel as claimed in the claims, wherein the corners formed by the intersection points are rounded.

2 The radius of curvature of the roundness given to the corner formed by the side wall of the groove on the entire cooling surface and the point between the cooling surface.

The method of casting cast steel as claimed in the claims.

3. The steel casting method according to the claims, wherein the depth of the entire cooling surface is 5 m@ or more.

Big,.

4 Cold L96. Tsuff groove. , □5. Outside□14. 1
For gold, the groove depth must be within 20 times, and the remaining cooled surface after groove cutting must be within 80%, and for inner side surface coating and bottom surface cooling, the groove spacing must be 12 times the groove depth. The cast steel casting method according to the claims, wherein the remaining cooled surface after grooving is within 70%.

5 The shape of the grooves provided on the entire cooling surface is changed to a grid-like shape □
A method of casting steel according to the claims, which forms a continuous pattern of triangles or hexagons.

6. The cast steel according to the claims, in which the shape of the grooves provided on the entire cooling surface is replaced by a lattice shape, and in which conical or truncated conical recesses are provided at positions corresponding to the apexes of a triangle or hexagon. Base system.

7. The shape of the grooves provided on the entire cooling surface has been changed to a lattice shape,
Cast w4 according to the claims, which has a spherical or truncated spherical recess at a position corresponding to the apex of a triangle or hexagon.
@Zoho.

8. When casting using chilled metal, apply a thickness of 5 on the entire cooled surface.
A cast steel casting method according to the claims, in which a mold coating agent of M or less is applied.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of grid-like grooves provided on the entire cooling surface, and FIG. 2 is a schematic diagram of the cross-sectional shape of the grooves. Figure 3 is a chart showing the crack prevention effect when grid-like grooves are provided on the entire surface of a flat dog-shaped cooler. Figure 4 shows triangular or hexagonal continuous pattern grooves. Schematic diagram of a dent. Figure 5 is a comparison diagram of the casting surface maintenance and repair process for the entire surface of a core with one curvature. Figure 6 shows a truncated conical depression (a) and a truncated spherical depression (b).
) is a schematic diagram. ■...Cold gold 2...Cold entire surface 3...
Groove 4...Casting surface 5...Groove side wall
6...Corner corner 7...Bottom of the groove 8.
...Dent A...Groove spacing F...Groove depth R
... Corner radius of curvature vs. 4 sides CC) Year 4 stroke (d) Figure 5 Bar 6 figure (α) (b) Procedural amendment (voluntary) March 30, 1980 Commissioner of the Japan Patent Office Young Kazuo Sugi 1, Indication of the case 1983 Patent Application No. 83261 2
, Title of the invention Steel casting method 3, Person making the amendment Relationship to the case Patent applicant Location
Address: Kato Building 4, 3-3-3 Nihonbashi, Higashisoto Chuo-ku
F Name (6193) Patent attorney Tatsuo Chanoki 5, Date of amendment order Showa 1920/Month/Day (Date of dispatch) 6, Subject of amendment Detailed explanation of the invention in the specification column 7, Contents of amendment 1 Description Next to “The effect is small” on page 9, line 10! two[
Insert "About hollow cylinders". □

Claims (1)

[Claims] 1. Casting is performed by forming desired unevenness on the cold metal surface of a cold metal used for part or the entire surface of the mold during casting of cast steel to divide the shrinkage stress of the casting surface. Steel casting method. 2 A grid-like groove is provided perpendicular to the chiller surface, the angle between several side walls and the chiller surface is 120° or more, and the corners formed by the intersections of the side walls and the chiller surface have curvature. A method for casting cast steel according to claim 1, wherein R is given. 3. The steel casting method according to claims 1 and 2, wherein grooves are formed to form a continuous square pattern on the chilled metal surface.